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1 | #include <linux/export.h> |
2 | #include <linux/sched.h> |
3 | #include <linux/fs.h> |
4 | #include <linux/path.h> |
5 | #include <linux/slab.h> |
6 | #include <linux/fs_struct.h> |
7 | #include "internal.h" |
8 | |
9 | static inline void path_get_longterm(struct path *path) |
10 | { |
11 | path_get(path); |
12 | mnt_make_longterm(path->mnt); |
13 | } |
14 | |
15 | static inline void path_put_longterm(struct path *path) |
16 | { |
17 | mnt_make_shortterm(path->mnt); |
18 | path_put(path); |
19 | } |
20 | |
21 | /* |
22 | * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values. |
23 | * It can block. |
24 | */ |
25 | void set_fs_root(struct fs_struct *fs, struct path *path) |
26 | { |
27 | struct path old_root; |
28 | |
29 | path_get_longterm(path); |
30 | spin_lock(&fs->lock); |
31 | write_seqcount_begin(&fs->seq); |
32 | old_root = fs->root; |
33 | fs->root = *path; |
34 | write_seqcount_end(&fs->seq); |
35 | spin_unlock(&fs->lock); |
36 | if (old_root.dentry) |
37 | path_put_longterm(&old_root); |
38 | } |
39 | |
40 | /* |
41 | * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values. |
42 | * It can block. |
43 | */ |
44 | void set_fs_pwd(struct fs_struct *fs, struct path *path) |
45 | { |
46 | struct path old_pwd; |
47 | |
48 | path_get_longterm(path); |
49 | spin_lock(&fs->lock); |
50 | write_seqcount_begin(&fs->seq); |
51 | old_pwd = fs->pwd; |
52 | fs->pwd = *path; |
53 | write_seqcount_end(&fs->seq); |
54 | spin_unlock(&fs->lock); |
55 | |
56 | if (old_pwd.dentry) |
57 | path_put_longterm(&old_pwd); |
58 | } |
59 | |
60 | static inline int replace_path(struct path *p, const struct path *old, const struct path *new) |
61 | { |
62 | if (likely(p->dentry != old->dentry || p->mnt != old->mnt)) |
63 | return 0; |
64 | *p = *new; |
65 | return 1; |
66 | } |
67 | |
68 | void chroot_fs_refs(struct path *old_root, struct path *new_root) |
69 | { |
70 | struct task_struct *g, *p; |
71 | struct fs_struct *fs; |
72 | int count = 0; |
73 | |
74 | read_lock(&tasklist_lock); |
75 | do_each_thread(g, p) { |
76 | task_lock(p); |
77 | fs = p->fs; |
78 | if (fs) { |
79 | int hits = 0; |
80 | spin_lock(&fs->lock); |
81 | write_seqcount_begin(&fs->seq); |
82 | hits += replace_path(&fs->root, old_root, new_root); |
83 | hits += replace_path(&fs->pwd, old_root, new_root); |
84 | write_seqcount_end(&fs->seq); |
85 | while (hits--) { |
86 | count++; |
87 | path_get_longterm(new_root); |
88 | } |
89 | spin_unlock(&fs->lock); |
90 | } |
91 | task_unlock(p); |
92 | } while_each_thread(g, p); |
93 | read_unlock(&tasklist_lock); |
94 | while (count--) |
95 | path_put_longterm(old_root); |
96 | } |
97 | |
98 | void free_fs_struct(struct fs_struct *fs) |
99 | { |
100 | path_put_longterm(&fs->root); |
101 | path_put_longterm(&fs->pwd); |
102 | kmem_cache_free(fs_cachep, fs); |
103 | } |
104 | |
105 | void exit_fs(struct task_struct *tsk) |
106 | { |
107 | struct fs_struct *fs = tsk->fs; |
108 | |
109 | if (fs) { |
110 | int kill; |
111 | task_lock(tsk); |
112 | spin_lock(&fs->lock); |
113 | tsk->fs = NULL; |
114 | kill = !--fs->users; |
115 | spin_unlock(&fs->lock); |
116 | task_unlock(tsk); |
117 | if (kill) |
118 | free_fs_struct(fs); |
119 | } |
120 | } |
121 | |
122 | struct fs_struct *copy_fs_struct(struct fs_struct *old) |
123 | { |
124 | struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); |
125 | /* We don't need to lock fs - think why ;-) */ |
126 | if (fs) { |
127 | fs->users = 1; |
128 | fs->in_exec = 0; |
129 | spin_lock_init(&fs->lock); |
130 | seqcount_init(&fs->seq); |
131 | fs->umask = old->umask; |
132 | |
133 | spin_lock(&old->lock); |
134 | fs->root = old->root; |
135 | path_get_longterm(&fs->root); |
136 | fs->pwd = old->pwd; |
137 | path_get_longterm(&fs->pwd); |
138 | spin_unlock(&old->lock); |
139 | } |
140 | return fs; |
141 | } |
142 | |
143 | int unshare_fs_struct(void) |
144 | { |
145 | struct fs_struct *fs = current->fs; |
146 | struct fs_struct *new_fs = copy_fs_struct(fs); |
147 | int kill; |
148 | |
149 | if (!new_fs) |
150 | return -ENOMEM; |
151 | |
152 | task_lock(current); |
153 | spin_lock(&fs->lock); |
154 | kill = !--fs->users; |
155 | current->fs = new_fs; |
156 | spin_unlock(&fs->lock); |
157 | task_unlock(current); |
158 | |
159 | if (kill) |
160 | free_fs_struct(fs); |
161 | |
162 | return 0; |
163 | } |
164 | EXPORT_SYMBOL_GPL(unshare_fs_struct); |
165 | |
166 | int current_umask(void) |
167 | { |
168 | return current->fs->umask; |
169 | } |
170 | EXPORT_SYMBOL(current_umask); |
171 | |
172 | /* to be mentioned only in INIT_TASK */ |
173 | struct fs_struct init_fs = { |
174 | .users = 1, |
175 | .lock = __SPIN_LOCK_UNLOCKED(init_fs.lock), |
176 | .seq = SEQCNT_ZERO, |
177 | .umask = 0022, |
178 | }; |
179 | |
180 | void daemonize_fs_struct(void) |
181 | { |
182 | struct fs_struct *fs = current->fs; |
183 | |
184 | if (fs) { |
185 | int kill; |
186 | |
187 | task_lock(current); |
188 | |
189 | spin_lock(&init_fs.lock); |
190 | init_fs.users++; |
191 | spin_unlock(&init_fs.lock); |
192 | |
193 | spin_lock(&fs->lock); |
194 | current->fs = &init_fs; |
195 | kill = !--fs->users; |
196 | spin_unlock(&fs->lock); |
197 | |
198 | task_unlock(current); |
199 | if (kill) |
200 | free_fs_struct(fs); |
201 | } |
202 | } |
203 |
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
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v3.9